Among the calamities of the 20th century were vast social experiments that tried to transform humanity with disastrous consequences. The Nazi experiment, based on the notion that evil is inborn in certain races, rejected education as a means of correction and instead pursued the extermination of millions of alleged incorrigibles. It drew upon a then-legitimate scientific tradition that had been widely accepted in Western countries for half a century. The Khmer Rouge experiment, based on the contrasting notion that complete "re-education" is possible, attempted to change the behavior of millions of Cambodians and killed them if they resisted change. Presumably their deaths would serve as salutary examples for survivors. Both these vicious programs, if they did not derive from theories of human nature, clearly derived comfort from them, and should lay to rest permanently the claim that such theories do not matter.

The question, of course -- after getting the right theories -- is how they should matter. Both of these books consider the implications for society of a new theory, which if it leans toward the inborn-nature side of the ledger does so in a more modest and sophisticated way than such theories have in the past. The importance of genes can no longer be denied. The genome has been sequenced, some diseases are yielding their secrets to genetic research and, in the realm of behavior, statistical studies are demonstrating genetic influences on everything from reaction time to religiosity and happiness. As for evolution, flat earthers are still denying Darwin, but in scientific circles he has won the day, and his theory and extensions of it are clearly more than a little relevant to behavior. Here, too, the approach bears little resemblance to the parallel efforts of the late 19th century. Finally, a revolution in brain science -- not least of all due to advanced techniques of brain imaging -- has removed all reasonable doubt as to the isomorphism of brain and mind. This is a direct extension of the 19th-century program in brain science, but it is much, much better.

These two books promise to help us think through the social implications of this great transformation. The first, Pinker's The Blank Slate, is the broader and more ambitious work, attempting to show how commitment to a tabula rasa view of human nature has misled the modern social sciences and therefore misled policy. If it sometimes seems to be flogging a dead horse, it is nonetheless a brilliant and forceful summary of the current evidence for biological influences on human social life.

Pinker reviews the blank-slate notion from John Locke to Margaret Mead, thoroughly demolishing it with evidence for the power of genes in behavior, evolution in culture, brain in mind. With equal cogency he also replies to challenges raised by recent advocates of blank slatism. How, for example, can the human genome, only twice as big as that of the near-microscopic roundworm, determine anything about our complex mental life? It can if we consider not just the number of genes but their interactions and hierarchical ordering. How can the human brain be less malleable than artificial neural networks, which have great capacity for learning? Because the brain has evolved over hundreds of millions of years and contains many pieces of dedicated circuitry -- some as old or older than the hills -- assembled largely by the genes.

In the philosophical core of his book, Pinker considers four feared outcomes of Darwinian theory: justifying discrimination, abandoning attempts to improve humanity, destroying free will and responsibility, and the loss of meaning and purpose from life. Each of these understandable fears, Pinker argues, is unfounded.

Asking if racism and sexism could be justified, he answers emphatically, "Absolutely not! The case against bigotry is not a factual claim that humans are biologically indistinguishable. It is a moral stance that condemns judging an individual according to the average traits of certain groups to which the individual belongs." Of course, if the average traits of certain groups do differ, that might lend support to "statistical discrimination." But in the case of race, Pinker points out that the biological differences are, in fact, trivial. Moreover, Jefferson's urging "that all men are created equal" was about rights, not sameness. Perfectibility, for its part, is enhanced by knowledge of our own natures. Furthermore, Pinker writes, a concept of human nature itself "provides a yardstick to identify suffering in any member of our species." It is because we have comparable natures that universal empathy for suffering is possible and universal notions of human rights valid.

As to responsibility, legal assessments increasingly entertain the argument that biological influences are exculpatory. But punishment also is an influence on human action that is mediated by the same brain that generated the crime. Both evolutionary and criminal psychologies suggest that the certainty of punishment turns the power of human nature against wrongdoing. Nor need biology drain life of meaning; Pinker cites Kant's awe at "the moral law within" as evidence of the opposite effect.

"A man has got to know his limitations," is the apt Clint Eastwood quote that sets the tone for the rest of the book, a well-informed and well-written account of those limitations. In a graceful interleaving of scientific and literary sources, Pinker takes us through some of what we know of our constraints. They are sobering. We unquestionably have selfish and violent tendencies, tempered mainly for our children and other close relatives and in reciprocal or gainful relations with others. For all our efforts at nurturance, Pinker finds little evidence that different styles of parenting significantly shape our children's personalities and behavior, instead ceding most causation to genes and peers. Unlike race, gender is a valid and significant biological and psychological category, which, despite huge overlaps between male and female, does help us predict some aspects of behavior and mental life.

The science dovetails with discussions of policy issues, and here Pinker is less helpful. For example, he quotes a Boston Globe columnist who asks, "So why is America more violent than other industrialized Western democracies?" The columnist gives a cultural answer, but Pinker proceeds to debunk all the usual cultural explanations. After explaining what he calls the "evolutionary logic of violence" -- which he does very well -- he goes on to say, "Human nature is the problem, but human nature is also the solution.") Alas, he only gives us evidence for the first half of that sentence, and he doesn't answer the Globe columnist's question. If Americans share the same human nature with people in much less (as well as much more) violent cultures, how can human nature explain the differences? This is not a minor problem; Pinker seems to believe that evolutionary biology has the answer to everything, but actually it can only be a starting point and, in some ways, a guide for a complex biocultural analysis, most of which depends on the same social-science approaches that have served us in the past.

But it's enough to ask Pinker to debunk blank slatism, trace its history and offer a more than competent summary of what we know now about what evolution and genes have written on the slate without asking him to solve the problems, too. Pinker is not a policy maker, nor does he have all the answers to our social ills. But he does know one big thing: No policies of any sort, in any realm of life, can fare well ignoring human nature. Do the European democracies with lower levels of violence achieve that result through policies that reflect an understanding of human nature? Perhaps not in the scientific sense, but Europeans in general have always tended to be more cynical than Americans, less sanguine, for better or for worse, about the possibility of change. Americans have often done well with our high expectations, but unless we come to terms with the limitations of human nature, they will continue to stand squarely in our way.

Paul H. Rubin's aim in Darwinian Politics is at once more modest and more ambitious. He focuses on political behavior but his aim, as the book's subtitle suggests, is to explain "the evolutionary origin of freedom." An economist by training, he came late to the biological banquet, but he has digested many things. His purpose is "to examine, from an evolutionary perspective, certain political behaviors and preferences common to humans." He succeeds admirably.

Rubin begins at the beginning, with an account of hunter-gatherer life in the human "environment of evolutionary adaptedness" (EEA). For most of our evolution we lived in small, face-to-face groups, surrounded mostly by kin and depending on others for sustenance through reciprocal relationships. There was little division of labor except by sex, but some men could dominate women and other men, and they passed on the genes for a number of unfortunate human behaviors. From this era also comes our easy commitment to groups and our willingness to devalue those outside them, sometimes to the point of violence. Violence within hunter-gatherer groups was also not uncommon, although mechanisms restricting violence -- sharing, talking, exchanging gifts and spouses -- were pervasive.

As we settled into agricultural and pastoral villages, gradually building them into what we are pleased to call civilization, the intensity and ubiquity of group conflict greatly increased. Conquest often entailed slaughter, usually of men. Women, especially young ones, were kept alive for partly reproductive reasons, and this pattern also may have had genetic consequences, although there has not been enough time since the rise of towns for much genetic change. If you doubt these patterns, you can read excellent new research in archeology and anthropology or, to save time, you can just reread the Bible.

The key question raised again and again in this well-crafted book is, "How well does a given kind of social or political order meet the needs we evolved in the EEA?" In the chapter on altruism, Rubin considers several extant explanations -- kin selection, cooperation, reciprocal altruism and group selection -- for the evolution of altruistic tendencies and shows how their legacy in human nature may be affecting us in the vastly larger-scale societies we live in now. For example, Rubin believes that Americans' dissatisfaction with the welfare system drew on our evolutionary distaste for shirkers and cheaters and grew until the adjustments of the late 1990s brought the system back into line with our evolved tendencies. This may seem satisfying, but it doesn't explain why the Scandinavians, with the same evolved tendencies, are still willing to countenance so much more welfare. The citizens of these mild, judicious welfare states are descended from Vikings; we may not know why they changed, but genes are not high on the list of plausible explanations.

Then, too, there is a Procrustean bed aspect to Rubin's use of the EEA. In the chapter on envy, for example, he argues that this emotion was highly adaptive during our evolution because it prevented others, regardless of skill, from becoming too dominant. Now, however -- the argument goes -- envy is maladaptive because the wealth of the few benefits the many. Aside from Rubin's credulity about the sources and consequences of wealth -- emphasizing productivity and frugality as means of wealth accumulation, he ignores inheritance, exploitation and cheating -- he has now used the EEA argument in two contradictory ways. We must modify the welfare system to encourage work because that satisfies the evolved human tendency to resent shirkers, but we must resist the evolved tendency to envy because, unlike the resentment of people on welfare, resentment of the rich is no longer adaptive. Here Rubin risks a convenient modification of the analysis to accommodate a certain political leaning.

Yet Rubin is no Hobbesian. He is careful to distinguish the desire of some individuals to accumulate wealth from the desire, all-too-often associated with it, to accumulate power. He correctly argues that throughout our evolution, dominance was advantageous but restricted, with the net result being that there was more freedom from the authority of strongmen than there has been for most of subsequent history. Given the ties that bind in a kin-based, face-to-face society, men at least were relatively free.

This leads to perhaps the most important point of the book. Contra Hobbes, autocratic society violates human nature for most of those who belong to it and therefore is inherently unstable. Rubin also argues, however, that libertarianism is unstable because it entails extremes of individuality that equally violate evolved human tendencies and thus cause social breakdown. What then is the pattern of political life most consistent with those tendencies?

This is where we have been moving all along, both in the world and in the book, and in broad strokes it roughly corresponds to the kind of polity we have in the United States today. (Oddly, he doesn't cite Hegel or Fukuyama, with whom he has an intriguing complementarity.) Rubin recognizes that this polity still needs to be made a lot better, and he is not unaware that even a semblance of fair play and freedom for all is a quite recent development. However, America's -- or, for that matter, Italy's or Sweden's or various other democracies' -- combination of respect for individuality, systematic restrictions on power, opportunity for the accumulation of wealth, relative perception of fair play and relatively high floor under the most disadvantaged reflects a surprising number of features of the kind of society we evolved in. Or, more precisely, it satisfies with different devices the same needs that evolved there and that remain with us still.

This is not an implausible argument; I have made it myself in these pages. But before we conclude that all's for the best in this best of all possible worlds, we should mention two caveats. First, there was no EEA; there were EEAs. Anthropologists are still trying to understand what the range of adaptations was, as a prelude to becoming more confident in inferring a central tendency. Second, and more important, democracy is a work in progress; many varied experiments in democracy are already under way, not to mention those to come.

It is one thing to say that our evolved human nature precludes a good life and a good society under either autocracy or libertarianism. It is quite another to try to cut the varied cloth of democracy much more finely using the relatively blunt instrument of what we know now about our evolved human nature. At the moment, I find John Rawls' theory of justice, which Rubin rejects, to be as consonant with what we know about the EEAs as Jeremy Bentham's utilitarianism, which he embraces. But we still have a lot to learn.

Yet these are quibbles. Both these fine books help with a task that we all must begin to take seriously. Pinker and Rubin suggest that we are ready to overcome the fruitless nature-nurture battles, which have generated so much more heat than light, and do the hard work of incorporating advances in biology into our thinking about political and social life. I am not an optimist, but these two books are encouraging. Can it be that we have finally grown up?

About the Author

Melvin Konner, the Samuel Candler Dobbs Professor of Anthropology and associate professor of Psychiatry and Neurology at Emory University, is the author of The Tangled Wing: Biological Constraints on the Human Spirit.